1. Field of the Invention
The present invention relates to an electronic parts mounting device and, more particularly, to an electronic parts loading device for mounting electronic parts such as semiconductors on a printed circuit board (PCB).
2. Description of the Prior Art
Generally, an electronic parts loading device is used to mechanically mount semiconductors such as integrated circuits (ICs) and large scale integration (LSI), diodes, condensers, resistors, etc. to a PCB.
A loading element for loading electronic parts on a printed circuit board, and a spreading element for applying an adhesive before loading onto the PCB are mounted to the electronic parts loading device.
The electronic parts loading device includes a guide rail for guiding the PCB to a fixed location, and a parts stage for supporting a plurality of electronic parts to be loaded on the printed circuit board.
The loading element and spreading element, both comprising a process element, are mounted to a head unit above the guide rail which moves horizontally along X and Y axes.
The process element moves to a loading position and a spreading position (hereinafter referred to as a process position) according to the movement of the loading element. Here, after the process element raises and moves to the process position, it then descends downward toward the PCB.
The PCB, carried in and positioned at a fixed location, often becomes warped and is seldom positioned evenly (i.e., where a distance between the PCB and the head unit is equal over the entire surface of the printed circuit board).
As a result of this frequent unequal distance between the PCB and head unit, the process element descends to a predetermined position without taking into account these discrepancies in distance. This often leads to the process element descending excessively or insufficiently with relation to the PCB.
If the loading element insufficiently descends, the loading element either incorrectly loads the electronic parts or is unable to load the parts to the PCB such that the loading element returns still engaging the electronic part. Also, a lead is not properly settled, or during reflow insufficient movement/loading develops.
If the loading element excessively descends, especially during high-speed loading, as load pressure is generated, the electronic parts can become damaged or pushed to the side such that the loading position of the electronic parts is not securely fixed.
If the spreading element insufficiently descends, the application of the adhesive material may not occur, the application area may not be adequately large, or the application state may not be firm.
Finally, if the spreading element excessively descends, especially when high-speed spreading for ceramic circuit boards etc., the PCB becomes damaged, noise is created, a deficient amount of adhesive material is applied, or the adhesive material is unevenly applied. In all of the above cases, the drawback of an insecure application state results.
To solve the problems of the process element insufficiently and excessively descending, an escape device is added to a loading bit, formed on an end of the loading element, to reduce the incorrect descending of the same, and by the use of a backup pin, the evenness of the PCB is maximized. Also, an adhesion needle and a stopper, which can move the entire up and down distance, are mounted to the spreading element. As a lower end of the stopper makes contact close to adhesive points on the PCB, the degree to which the stopper descends must be set.
As in the above, if an escape device is mounted to the loading element, because it is adhered to a moving part side, careful consideration is required to maintain accuracy, and when moving at high speeds, the added weight from the escape device on the loading element causes shocks.
Also, if a backup pin is used, it is difficult to make the PCB perfectly even because there are individual differences between each PCB. And because a separate suction device is needed to prevent warping of the PCB, the overall structure of the loading device becomes complicated.
Further, if a stopper is mounted to the spreading element, as the adhesion needle is generally connected with a syringe, and even if the escape device is mounted to a drive element for driving the spreading element, the weight of the moving part is greatly increased so as to hinder the speed of the loading device. A drawback results such that the head unit must be rotated to enable a bottom end of the stopper to adhere to points of adhesion and to the loading parts.
With regard to the operation of the process element on the PCB, the process element is raised and moved to the process location, both loading and application locations, by the head unit, and after the process location is reached the process element is advanced downward toward the PCB. An end of the needle is placed at the application location in the spreading element and wetted with application material. Further, according to the degree to which electronic parts are pressed to the adhesive material, reflow solder is realized.
Because electronic parts must be precisely mounted on the PCB, the adhesive material must also be precisely placed. Accordingly, a center of the needle cannot be inaccurately placed because this will result in the imprecise placing of the adhesive material.
Here, for reasons of efficiency and ease, recharging after using the electrically charged adhesive material is generally realized by exchanging the entire syringe. As the syringe and needle are integrated as a single piece, the position of the end of the needle must be re-adjusted every time the syringe is exchanged. The re-adjusting process is further complicated due to the fact that there are a variety of syringe and needle sizes. In addition, when two needles (i.e., twin needles) are used for the application of the adhesive material in two places simultaneously, the positioning of the needles becomes much more arduous.
To solve this problem, an attachment is used for maintaining a center location of the needle even if there are changes in the size of the needle when exchanging the syringe.
However, the structure of the loading device is complicated when using an attachment because changes must be made to allow the exchanging of the attachment. As a result, the overall cost of the loading device is increased and the process is made difficult as the attachment must be changed if the size of the needle is different.